Protection From Corrosion; Protecting The Unit From Frost - Hitecsa EQS 2335 Manual Del Usuario

II.7.4

Protection from corrosion

Do not use corrosive water containing deposits or debris; The corrosive
limits for braze-welded stainless steel exchangers are found below:
pH
SO4--
HCO3-/SO4--
Total hardness
CI-
PO43-
NH3
Fe+++
Mn++
CO
2
H S
2
Temperature
Oxygen content
Alkalinity (HCO )
3
Electrical Conductivity
Nitrate (NO )
3
If you are not reasonably sure of the water quality in the table above or
if there are doubts concerning the presence of different materials which
could corrode the heat exchanger over time, it is always advisable to
insert an intermediate heat exchanger which can be inspected, made of
materials that are able to resist these substances.
II.7.5

Protecting the unit from frost

II.7.5.1 Indications for unit when not running
IMPORTANT!
If the unit is not used during the winter period, the
water contained in the system may freeze.
The entire circuit must be drained in good time. A drainage point below
the water exchanger must be used to make sure all the water empties
out. Moreover, use the valves placed in the lower part of the water
exchanger so that is empties completely.
If the draining operation is felt to be too much trouble, ethylene glycol
may be mixed with the water in suitable proportions in order to
guarantee protection from freezing.
Units are available with an antifreeze heater (PA accessory) to keep the
evaporator intact, should the temperature drop excessively.
IMPORTANT!
The unit must not be isolated from the electrical
power supply during the entire seasonal stoppage
II.7.5.2 Indications for unit when running
The use of ethylene glycol is recommended if you do not wish to drain
the water from the hydraulic system during the winter stoppage, or if the
unit has to supply chilled water at temperatures lower than 5°C (the
latter case, not considered here, depends on the size of the unit
system).
Table "H" shows the multipliers which allow the changes in performance
of the units to be determined in proportion to the required percentage of
ethylene glycol.
The multipliers refer to the following conditions: condenser inlet water
temperature 35°C; chilled water outlet temperature 7°C; temperature
differential at evaporator and condenser 5°C.
7.5 ÷ 9.0
< 70 ppm
> 1.0 ppm
4.0 ÷ 8.5 dH
< 50 ppm
< 2.0 ppm
< 0.5 ppm
< 0.2 ppm
< 0.05 ppm
< 5 ppm
< 50 ppb
< 65 °C
< 0.1 ppm
70 ÷ 300 ppm
μS/cm
10 ÷ 500
< 100 ppm
For different functioning conditions, the same coefficients can be used
as their variations are negligible.
IMPORTANT!
Mixing the water with glycol modifies the
performance of the unit
Table "H"
Design air temp.
2
in °C
% glycol in
10
weight
Freezing tem p.
-5
°C
fc G 1,025 1,039 1,054 1,072 1,093 1,116 1,140
fc ∆pw 1,085 1,128 1,191 1,255 1,319 1,383 1,468
fc QF 0,975 0,967 0,963 0,956 0,948 0,944 0,937
fc P 0,993 0,991 0,990 0,988 0,986 0,983 0,981
= Correction factor of the glycol water flow to the evaporator
fc G
fc ∆pw = Correction factor of the pressure drops in the evaporator
fc QF = Cooling capacity correction factor
= Correction factor for the total absorbed electrical current.
fc P
Use of anti-freeze solutions with the BT accessory
The table provides the percentage of ethylene/propylene glycol to be
used in units with the BT accessory, according to the temperature of the
chilled water produced. Use the HITECSA UpToDate Software for unit
performance.
Outlet temperature
glycoled water
evaporator
From -7,1°C a -8°C
From -6,1°C to -7°C
From -5,1°C to -6°C
From -4,1°C to -5°C
From -3,1°C to -4°C
From -2,1°C to -3°C
From -1,1°C to -2°C
From -0,1°C to -1°C
From 0,9°C a 0°C
From 1,9°C to 1°C
From 2,9°C a 2°C
From 3,9°C to 3°C
From 4,9°C to 4°C
66
EQS
0 -3 -6 -10
15 20 25 30
-7 -10 -13 -16
Minimum % glycol Minimum % glycol
in weight in weight
33
32
30
28
26
24
22
20
20
18
15
12
10
-15 -20
35 40
-20 -25
34
33
32
30
28
26
24
22
20
18
15
12
10